RU2547796C1 - Electric cardiac pacemaker - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: electric cardiac pacemaker comprises a microprocessor control unit, three digital-to-analogue converters, an output of the first converter is connected to the first input of a multi-channel analogue switch, an output of the second converter is connected to its input and through an inverter to the third converter. An output of the third converter is connected to a control input of a controlled resistor coupled to a feedback circuit of an adder amplifier. Three inputs of the adder amplifier are connected to outputs of the multi-channel switch and its output is connected to the input of a power amplifier. An output of the adder amplifier is connected to operating electrodes. Control inputs of digital-to-analogue converters and analogue switches are connected to bus bars of the microprocessor control unit. In the electric cardiac pacemaker there are three additionally introduced counters/timers connected through control bas bars to the microprocessor control unit. Inverting inputs of the two first counters/timers are connected through the amplifier and galvanic isolation circuit to a heart beat sensor. An inverting input of the third counter/timer is connected to a system clock source of the microprocessor control unit.

EFFECT: usage of the invention allows an improvement in efficiency of electric stimulation due to synchronised switching of the main operation modes with the heart beat of a patient.

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Description

The invention relates to medical equipment and can be used for electrotherapy with diadynamic and modulated currents of various shapes, frequencies, duty cycle and modulation method.

A number of devices for physiotherapy are known: "SNIM-1" [Apparatus for low-frequency therapy with sinusoidal modulated pulses SNIM-1. Passport], Tonus-2M [Apparatus for low-frequency therapy with sinusoidal modulated pulses Tonus-2M. Passport], "DT-50" [Apparatus for the treatment of diadynamic currents "DT-50" Passport].

All of them contain:

- a rectifier forming a sequence of sinusoidal pulses of frequency 50 Hz (half-wave rectification) and 100 Hz (half-wave rectification),

- a modulator that provides modulation of the current with a short period, modulation with a long period of a single-cycle wave current and a push-pull wave current, which are modulated not only in frequency but also in amplitude,

- shaper, forming an exponential decay of sinusoidal pulses with a frequency of 50 and 100 Hz,

- switch types of current, providing alternating current in accordance with a given modulation mode,

- shaper modulation intervals, providing the required intervals of the alternation of frequencies,

- a clock generator that determines the discreteness of the modulation intervals,

- an output current regulator providing the required current level,

- output electrodes applied to the patient

[Livenson A.R. Electromedical equipment, 5th ed., Revised. - M.: Medicine, 344 p.].

The disadvantages of these devices include limited functionality, low safety stimulation associated with the lack of current protection, high weight and dimensions, the complexity of outdated circuitry solutions, due only to the analog (without the use of digital methods) implementation of the operating modes.

Another disadvantage is the lack of synchronization of switching of the main modes of operation with the patient’s heart rhythm, which reduces the effectiveness of treatment and tolerance of the physiotherapeutic procedure.

A known biosynchronization system for physiotherapeutic and destructive processes of influence, comprising a pulse sensor connected through the first amplifier to the input of the first control unit, the output of which is connected to the control input of the first switch, a breathing sensor connected through the second amplifier to the input of the second control unit, the output of which is connected to the control the input of the second switch, and the first and second switches are connected in a series circuit between the output of the physiotherapeutic or destructive source of the process of exposure and the object of exposure or made with the possibility of sequentially blocking or rejecting the flow of the physiotherapeutic or destructive process of exposure using the appropriate mechanical interrupter or curtain [RF Patent N2186584, cl. A61N 1/00, A61B 17/00, “System biosynchronization of physiotherapeutic and destructive processes of exposure”].

The device provides synchronization of the main operating modes with biorhythms of the patient, however, it has a complex circuitry, primarily due to the use of purely hardware implementation, and does not provide for the possibility of operational (software) change in the waveform and low-frequency envelope.

The closest in technical essence to the invention is an electrical stimulator containing a microprocessor control unit, three digital-to-analog converters connected to the control bus of the microprocessor unit and designed to generate exposure signals, their amplitude and mixed modulation, a multi-channel analog signal switch, the outputs of which are connected to the inputs of the summing amplifier and the inputs - with the outputs of the first two digital-to-analog converters and with the output of the inverter of polarity, the output of the third the digital-to-analog converter is connected to an adjustable resistance control input connected to the signal amplitude control circuit at the output of the summing amplifier, the output of which is connected to the input of the power amplifier connected to the input of the blocking unit, with the input of the initial-current protection unit and the input of the on-off switch, the input of which is connected to the output of the logical inverter, the normally-closed contact of the key is connected to the output of the resistor, the normally-open contact is connected to the anode-electrode, the cathode-electrode is connected to each other they output a resistor and the input of the overcurrent protection unit, the output of which is connected to the initial installation bus of the microprocessor control unit [RF Patent N2121380, cl. A61N 1/36, “Electrostimulator”].

The advantage of the device is the ability to quickly change the shape of the stimulation signals and an increased level of patient safety, provided through the use of software and hardware.

The disadvantage of this device is the lack of synchronization of switching the main modes of operation with the patient’s heart rate, which reduces the effectiveness of physiotherapy.

The technical result of the invention is to increase the efficiency of electrical stimulation by synchronizing the moments of switching the main modes of operation with the patient’s heart rhythm.

The essence of the invention lies in the fact that in an electrical stimulator containing a microprocessor control unit, three digital-to-analog converters, the output of the first one is connected to the first input of a multichannel analog switch, the output of the second is connected to its second input and through the inverter to the third, the output of the third converter is connected to the control input of the controlled resistor included in the feedback circuit of the amplifier-adder, the three inputs of which are connected to the outputs of the multi-channel switch, and the output with the input of the amplifier the output of which is connected to the action electrodes, the control inputs of the digital-to-analog converters and the analog switch are connected to the buses of the microprocessor control unit, three additional counters / timers are introduced, connected via the control buses to the microprocessor control unit, the counting inputs of the first two counters / timers are connected through an amplifier and galvanic isolation circuit to the heart rate sensor, the counting input of the third counter / timer is connected to the source of the system clock a microprocessor control unit.

Figure 1 presents a block diagram of a device. The device comprises a microprocessor control unit (MBU) 1, three digital-to-analog converters 2, 3, 4, connected to the microprocessor control unit 1 via buses I, II, IV, a polarity inverter 5, a multi-channel analog signal switch 6, connected to the microprocessor control unit 1 through bus III, amplifier-adder 7, controlled resistor 8, power amplifier 9, exposure electrodes 10, heart rate sensor 11, galvanic isolation device 12, amplifier / driver of the heart rate sensor 13, two are programmable x counter / timer (C / T) 14, 15, the counting inputs of which are connected to the output of the amplifier / signal generator of the heart rate sensor 13, the third counter / timer 16, to the counting input of which the clock signals of the system generator MBU 1 are supplied, all counters / timers connected to the microprocessor control unit via the programming buses of the operation mode of the timers / counters and monitoring their status V, VI, VII.

The device operates as follows.

The task of a specific type of stimulating current I _c , as in the prototype, is determined by a combination of various parameters: frequency, shape, presence of frequency, amplitude or mixed modulation, and is carried out in accordance with the program stored in the resident memory of the MBU.

Unlike the prototype, the reproduction of these parameters occurs in concert with the heart rate, and not with the independent stable frequency generated by the MBU. Heartbeat pulses are removed from the heart rate sensor 11, through a galvanic isolation device 12, which protects the patient from damage by mains voltage during emergency conditions, are amplified by an amplifier / driver 13, which ensures the reliability of digital devices, and are fed to the inputs of two additional counters / timers 14, 15, the first of which forms a sequence of time intervals that determine the duration of exposure to signals of a given shape in accordance with the selected mode, the second etchik / timer measures the repetition period of the heart rate, the duration required for the correction information selecting sampling clock cycles from the digital to analog converters 3 and 4, the pulse modulation signals forming exposure.

The choice of the operating mode is carried out by the doctor. For each mode, the MBU determines the area of resident memory, which stores a digital image of the shape of the impact signals implemented using digital-to-analog converters, and the time intervals through which the shape of the impact signals is changed.

As an example, let us consider the formation of three types of exposure current characteristic of electrotherapy with diadynamic currents [Livenson A.R. Electromedical equipment. - M .: Medicine], namely, the Syncope rhythm (Fig. 2a), a single-cycle wave without amplitude modulation (Fig. 2b) and with amplitude modulation (Fig. 2c).

The classic mode of Syncope rhythm is characterized by a periodic change of pulse signals of exposure with a period of 2 seconds. in the first half-cycle, a burst of pulses of a given shape (most often with an exponential decay) is generated by the first digital-to-analog converter, the output of which is connected to the first input of the summing amplifier using an analog switch, the outputs of the second and third digital-to-analog converters are zeroed, and in the second, the exposure signal is removed. In the prototype, time intervals are formed from an independent clock and are not associated with the duration of heart rhythms.

In the proposed device, the half-cycle duration equal to the heart rate period is set by the counter / timer 14. In the Sinkop rhythm mode, it is programmed to operate with a conversion factor 1. The signal sampling intervals from the output of the first digital-to-analog converter are generated using the frequency ft of the internal system clock generator MBU.

When single-cycle wave mode (Fig.2B), the exposure period is divided into two unequal time intervals. In the first interval of duration n1T, a burst of pulses of a given shape is formed, generated by the first digital-to-analog converter and modulated by a low-frequency envelope signal, the shape of which is specified by the second DAC. In the second time interval n2T, the action signals are removed.

As in the previous case, in prototypes all time intervals are set in seconds. In this device, time intervals are determined by the number of periods of heartbeats. The first interval is defined as n1T _P , and the second as n2T _P , where T _P is the period of the heart rhythm. Accordingly, at the beginning, the counter / timer 2 is programmed using the MBU for the conversion factor n1, and after the end of the first interval it is reprogrammed for the conversion factor n2. During the first interval, stimulating pulses generated by the first DAC are fed to the first input of the summing amplifier through an analog switch, and the envelope voltage is fed to its second input. The summation of these two signals provides the desired waveform exposure. The shape of the envelope is set by the second DAC, which is determined by a set of N code combinations recorded in the resident memory of the MBU that are read when the desired signal is generated. The sampling period can be defined as

Δt = n1T _P / N.

As can be seen from the above formula, when using a heart rate period, the value of which is not constant, to form a sampling period, it is necessary to measure the value of T _P , for which a second timer is introduced into the proposed device (15). The obtained value is entered into the third counter / timer (16), which will form the required sampling period

Δt = n1T _P / N = (N _ST ) · (1 / ft),

whence the number N _CT loaded into the C / T3 comparison register to provide the required sampling time for a given number of samples N is defined as

N _CT = (n1T _P / N)

So at a clock frequency of ft = 10 · 10 ⁶ Hz, for n1T _P = 6 s, the comparison counter will require N _CT = 60000.

Thus, the introduction of the second and third counter / timer ensured the independence of the number of discrete samples from changes in the period of the heart rhythm.

To generate signals using amplitude modulation (Fig. 2c), the third DAC is used to form the envelope, the output of which is fed through an analog switch to the input of the amplitude controller.

The device can practically be implemented on the basis of modern microcontrollers, which ensures the implementation on one chip of all programmable components of the device, including the control bus shown in figure 1.

All programmable nodes of the device (digital-to-analog converters, counters / timers, control buses) shown in Fig. 1 can be implemented on a single chip of a modern microcontroller, for example STM32F37x, with an ARM ™ -Cortex-M4 microprocessor core (MBU), with three integrated digital-to-analog converters and seventeen 16- and 32-bit counters / timers.

In order to compare the results of treatment with the Tonus-1 device with the results of treatment using the proposed device, 2 groups of patients with a diagnosis of vertebrogenic cervicalgia were selected. Each group consisted of 20 people. (10 men from 32-65 years old and 10 women from 27-60 years old).

In both groups, a technique was used with the application of 2 symmetric electrodes on the collar zone. The anode was placed on the area with greater pain sensitivity, the cathode was symmetrically on the opposite side. A heart rate sensor was put on the patient’s finger. The duration of the procedure is 7 minutes, according to one procedure per day, in quantity - 10 procedures, with a current strength of 2 to 4 mA. The increase in current was determined individually, based on the pain of the patient. For objectivity in assessing the result and determining the psychoemotional state of patients in the control group (treatment with the Tonus-1 device) and in the experimental group (treatment with the proposed device), the Hopkins symptom questionnaire, the DN-4 questionnaire, C. Spielberg’s self-assessment and anxiety scale, and the Beck questionnaire ; for pain assessment - a comprehensive pain questionnaire, a scale for a five-point assessment of vertebral neurological symptoms.

When examining patients at the beginning of treatment, pain was noted - 70-80% on a visual analogue scale for assessing pain, limiting the angle of extension and flexion in the cervical spine 45-50 degrees, the angle of lateral tilt - 20 degrees, the angle of rotation - 50 degrees.

After treatment using the Tonus-1 device, the pain syndrome decreased to 40-50%, the recovery angle of extension and flexion was 55-65 degrees, the angle of inclination was 25 degrees, the rotation angle was 60 degrees.

In the group of men and women, the result did not differ.

After treatment using the proposed treatment device, the pain syndrome decreased to 10-20%. The effect is 45% higher than in the 1st study, the restoration of extension and flexion in the cervical spine angle of 75-80 degrees. 25-30 degrees more than in the 1st study. The lateral angle of 35 degrees (15 degrees more than with the 1st treatment), a turn of 70-75 degrees (also 15 degrees more than the first treatment).

In the female group, the treatment effect was 15% higher than the male due to the milder effect of the device.

Thus, as a result of the biosynchronization used in the treatment with the proposed device, patient tolerance to the procedures was significantly higher than during treatment with the Tonus-1 device, which allowed to reduce the duration of treatment and increase the therapeutic effect by 15-40%. In the second study, a group was recruited with a diagnosis of dorsopathy, vertebrogenic lumbalgia (pain in the lumbar spine). The identical treatment technique described above was applied, but with the application of electrodes on the lumbar region. After the course of treatment, patients showed a decrease in pain to 65-75% of the initial, increased mobility in the lumbar when turning the body with fixation of the pelvis and legs by 15-20 degrees from the original. The effect of synchronizing current pulses with the patient’s heart rhythm made it possible to ensure the necessary balance of the sympathetic and parasympathetic tone of the nervous system, which helps to increase the effectiveness of the procedures.

Claims (1)

An electrical stimulator containing a microprocessor control unit, three digital-to-analog converters, the output of the first of them is connected to the first input of a multichannel analog switch, the output of the second is connected to its second input and through the inverter to the third, the output of the third converter is connected to the control input of a controlled resistor included in the circuit feedback amplifier-adder, the three inputs of which are connected to the outputs of a multi-channel switch, and the output to the input of the power amplifier, the output of which is connected to the electrode effects, the control inputs of digital-to-analog converters and an analog switch are connected to the buses of the microprocessor control unit, characterized in that three additional counters / timers are introduced, connected via the control buses to the microprocessor control unit, the counting inputs of the first two counters / timers are connected through an amplifier and a galvanic isolation circuit to the heart rate sensor, the counting input of the third counter / timer is connected to the source of the microprocessor system clock Lok management.

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